The P.I. has established a cell-free system for the assembly of immature HIV-1 capsids that resemble immature particles by several biochemical and morphological criteria. Particle assembly in the system appears to proceed through several discrete intermediates and has been shown to be dependent on ATP, myristylation, and a cellular factor. In addition, antibody against the eukaryotic cytosolic chaperonin TCP-1 has been found to recognize Gag proteins in the cell-free lysates, suggesting that a TCP-1 related protein is associated with assembly intermediates. The P.I. proposes to use the system to study the mechanism of viral RNA encapsidation (AIM #1) and to define the role of assembly intermediates (AIM #2). Aim #3 is to purify the TCP-1 related protein in order to obtain high affinity antibodies and functional proteins that can be used in inactivation, depletion and reconstitution experiments that define the TCP-1 role.